Field of the Invention
The invention relates to an energy-generating installation, in particular a wind power installation, with a drive shaft connected to a rotor, a generator, and with a differential transmission with three drives and outputs, a first drive being connected to the drive shaft, one output to a generator, and a second drive to an electrical differential drive, and the differential drive being connected to a network via a frequency converter.
The invention furthermore relates to a method for operating an energy-generating installation, in particular a wind power installation, with a differential transmission with an electrical differential drive, the differential drive being connected to a network via a frequency converter with a DC intermediate circuit.
Description of the Related Art
Wind power installations are becoming increasingly important as electricity-generating installations. For this reason, the percentage of power generation by wind is continuously increasing. This in turn dictates, on the one hand, new standards with respect to current quality (especially with respect to reactive current control and behavior of the wind power installations during voltage dips in the network) and, on the other hand, a trend to still larger wind power installations. At the same time, a trend is recognizable toward offshore wind power installations, which trend requires installation sizes of at least 5 MW installed power. Due to the high costs for infrastructure and maintenance and repair of wind power installations in the offshore region, here, both efficiency and also production costs of the installations with the associated use of medium-voltage synchronous generators acquire special importance.
WO2004/109157 A1 shows a complex, hydrostatic “multipath” concept with several parallel differential stages and several switchable clutches, as a result of which it is possible to switch between the individual paths. With the technical design shown, the power and thus the losses of the hydrostatics can be reduced. One major disadvantage is, however, the complicated structure of the entire unit. In this case, the electrical energy fed into the network comes exclusively from the synchronous generator driven by the differential system.
EP 1283359 A1 shows a 1-stage and a multistage differential transmission with an electrical differential drive that drives—via a frequency converter—an electrical machine that is mechanically connected to the network-coupled synchronous generator. In this example, the electrical energy fed into the network also comes exclusively from the synchronous generator driven by the differential system.
WO 2006/010190 A1 shows the drive line of a wind power installation with an electrical differential drive with a frequency converter that is connected to the network parallel to the synchronous generator.
These technical designs do allow the direct connection of medium-voltage synchronous generators to the network; the disadvantages of known embodiments are, however, that differential systems with an electrical differential drive according to the state of the art are not able to reliably compensate for network voltage dips.